The present invention relates to generator cooling and, more particularly, to a baffle plate for guiding cooling gas and improving end-core ventilation.
During the process of producing electricity, power generators also create heat that must be dissipated away from the generator. Generators are typically gas-cooled by ventilated cooling systems that circulate cooling gas through ducts in the rotor and stator. By way of example, FIG. 1 schematically shows a partial cross-section of a generator having a reverse flow ventilation scheme. In the schematic illustration of FIG. 1, the rotor is generally shown at 10. The generator stator core 12 is constructed by stacking many layers of magnetic laminations. Ventilating ducts are defined between the stacked layers of magnetic laminations by providing spacers in the core stack. This allows for the passage of cooling gas through the core during operation. These spacers must be positioned in such a way to ensure tightness of the core during assembly and operation, but must not block or restrict the flow of gas through the stator. Outside space blocks 14 are located at the ends of the generator stator core, between the stacked laminations 16 and the stator flange 18, as schematically shown by dashed lines next to the flange 18 in FIG. 1. As illustrated, the cooling gas flow through the ventilation ducts between the stacked layers of laminations of the stator flows into the rotor-stator gap 20 to define a rotor-stator gap flow 22.
Cooling is one of the major challenges in conventional air-cooled generator designs as the rating of the machine is continuously increased. Analysis shows that extra eddy current losses in the end core of the machine are concentrated in the first package. In this regard, FIG. 1 illustrates the conventional air flow distribution in the region of the flange and the first package. As illustrated, air recirculation 24 has been observed in the region next to the first tooth 26 so that the first package 28 is not effectively cooled. The tooth temperature rise, as a result of the eddy current losses, often results in the hottest resistance temperature detector (RTD) temperature at the core end. Thus, it would be highly desirable to more effectively cool the first package 28 and flange 18 to improve the overall ventilation performance of the machine.
In an embodiment of the invention, a baffle is provided to guide the outside space block cooling gas all the way to the stator core inner diameter. The baffle provides a cost-effective method to effectively cool the first package by preventing hot air recirculations that conventionally occur at the tip of the flange and next to the first tooth. The baffle will also improve the heat transfer between the cooling gas and flange.
Thus, the invention is embodied in an electromagnetic generator comprising a stator structure concentrically disposed to a rotor structure, said stator structure having a radially outer surface and a radially inner surface, and including stacked laminations and an end flange component mounted to at least one axial end of said stacked laminations; a plurality of space blocks mounted between said stacked laminations and said end flange component, said space blocks being circumferentially spaced and extending radially to define a plurality of radial flow passages therebetween; and a baffle plate secured to said end flange component to extend radially inwardly from said end flange component substantially to said stator structure radially inner surface, a radially inner edge of said baffle plate including a plurality of slots for receiving copper end turns of said stator structure, whereby cooling air flowing between said stacked laminations and said end flange is directed substantially to said radially inner surface of said stator flange.
The invention may also be embodied in a method for controlling ventilation flow in a generator comprising providing a stator structure concentrically disposed to a rotor structure, said stator structure having a radially outer surface and a radially inner surface, and including stacked laminations and an end flange component mounted to at least one axial end of said stacked laminations, a plurality of space blocks being mounted between said stacked laminations and said end flange component, said space blocks being circumferentially spaced and extending radially to define a plurality of radial flow passages therebetween; providing a baffle plate structure; securing said baffle plate structure to said end flange component so as to extend radially inwardly from said end flange component substantially to said stator structure radially inner surface, a radially inner edge of said baffle plate including a plurality of slots for receiving copper end turns of said stator structure; and directing cooling air to flow between the stacked laminations and the end flange component and guiding the cooling air with said baffle plate to cool a radially inner portion of a first said lamination.